Phase-sensitive detector



. Aug. 5, 1947. J. E. sHEPl-uamaA 2,425,009 i PHASE-SENS ITIVE DETECTOR Filed June 29, 1943 676ML VOL 7465 Patented Aug. 5, 1947- i y A n I n .a y.

UNITED STATES BATEN T GFFICE f 2.425.069 PHASE-SENSITIVE DETECTOR .lames n. shepherd. Hempstead, N. Y., mmm in. Sperry Gyrosoopc Company, Inc., a corporation l voflilework iA Application June 29, 1943, Serial No.` 492,730

4 claims. (ci. i12- 245) My invention relates to phase responsive sys- Fig. 2 is a circuit diagram of anoth'er emboditems and electronic circui ment of the invention. p a

An object of the invention is to provide an im` Like reference characters are utilized throughproved phase detector and to provide phase reout the drawing to designatelike parts. sponsive systems in which no voltage or current s The illustrative arrangement vshown in Fig.` 1 mixing is required to take place in rectier elecomprises a pair of current controlling devices ments. such as double-triode vacuum tubes I'I and I2 A further object of my invention is lto provide for combining input voltages from two pairs of phase responsive systems in which no translinput terminals such as reference voltage termiiormers are required and in which full wave aclo nais-I3, I4 and signal voltage terminals I5 and tion may be obtained. l I6, the latter of which may be grounded, if de- Still another object of the present invention is sired. Associated with the voltage combining to provide a. phase responsive 'system which istubes II and I2 are combining transformers I 'I fully electronic and in which amplification may and I8, respectively, and unilateral conducting be obtained simultaneously with phase detection. 15 elements such as bi-phase connected rectiers I9v vOther and further objects and advantages will and 2I for rectifying the secondary outputs" of become apparent as the description proceeds. the transformers Il and I 8, respectively. The

In carrying out my invention in one preferred rectiilers I9 and 2| are connected, as will be exform thereof, I provide two units for combining plained hereinafter, for diierentiallyl supplying two voltages to be compared in phase withl the 20 th'eir outputs to a pair of direct current output phase relationship of one of the voltages reversed terminals 22. in one of the combining units. Inaddition, I For adjusting the magnitude of the reference provide means for rectifying the outputs of the voltage between terminals I3, I4 tothe most satiscombining units and combining said outputs in factory. value for application to the tubes II and opposed relation so that 'the net output varies in 25 I2, a potentiometer 23 may be provided comprismagnitude and polarity in accordance with the ing a resistor with a sliding tap 24. The tap 24 .variations in phase relationship between the inserves as one output terminal for the potentiput voltages. f ometer 23 and a second output terminal may be In carrying out my invention in accordance provided taking the form of a second sliding tap with another preferred form thereof, I utilize 80 or a fixed terminal 25, as illustrated. The ilxed a pair -of push-pull connected amplifiers, each terminal is satisfactory if the voltage between the having two separate control elements such' .as terminals I3 and I4 is floating so, that noY balcontrol grids and screen grids. Means are proance with respect to ground is required for the vided for supplying one input voltage such as a voltage between Ethe terminals 24, 25. reference voltage to the one set of grids connected g5 A reference voltage input circuit is completed push-pull, with the connections in one push-pull through input resistors 26 and 21 included in amplifier having the opposite polarity from those one of the grid circuits of the tubes II and I2, in the other. Means are also provided for suprespectively. An input resistor 28A is connected plying a second input such as a signal voltage to. across the signal terminals I5 and I6. the second set of grids with parallel input con- 40 'I'he tube II comprises a triode unit 29 consist- :nections instead of push-pull input connections ing ci' an anode 3|, a cathode '32, and a control but with opposite phase relation in the two amplielectrode or grid 33; and the second triode unit ilers. The amplifiers are connectedwith' parallel 33 comprises an anode 35, a cathode 36, and a push-pull plate loads so that the differential out-vr control electrode or grid 31. put varies in polarity and magnitude in accord- 45 The triode units 29 and 34 have a common ance with the variations in phase relationship cathode resistor 38 connected through a tap 39 between the input voltages. to an adjustable point in a potentiometer 4I for Abetter understanding of the invention will-be' vlalala'nzin'g the loads of the cathodes 32 and 36. afforded by the following detailed description The reference voltage input resistor 26 is included,` considered in connection with the accompanying 5I) in the grid circuit of the triode unit 2'9 which drawing, and those features of the "invention may include also a series grid resistor 43. The which are believed to be novel and patentable signal voltage input resistor28 is included in the will be pointed out in the claims appended hereto. grid circuit of the triode unit 34 'which may also In the drawing, I include a series grid resistor M. Fig. 1 is a circuit diagramA of one embodiment 56 The signal voltage input resistor 28 is conof myinvention. and nected in the same relation to a triode unit l5` of the triode units29` and vthrough the transformer winding parts 41 `and forming one-half oL the tube I2. The reference voltage input resistor 21 is connected in the input circuit of a second triode unit 46 forming the other half of the tube I2, but the connections are suchthat thejreference voltage is supplied with opposite perennes to the mode units 2s and 46. d"It will be understood of course, Ithat the signal voltage and the reference voltage may be interchanged so that the reference voltages are applied with like polarities to a pair of triode units and the signal voltages are applied with opposite polarities toA a pair *of triode units',

The current combining transformer I1 has two primary winding means such as a split primary winding with two parts 41 and 48 having a junction terminal 49; and the transformerI1 also has a split secondary winding with two parts I and 52 with a junction terminal 53. For supplying discharge current torr the tube II, a suitable source of current represented by'a battery 54 is provided. Thepositiveterminal of the battery 54 is connected to the transformer primary mid-terminal 49, whereby the discharge currents 34 flow separately 48, respectively. `The negative terminal of the battery 54 may be grounded in` the grounded system illustrated.. in which thel cathode returns and the resistor 28 are grounded.

The transformer I8 has windings connected to the tubes I2 and 2|, in amanner analogous to the connections of the transformer I1. n

.Although the loi-phase rectier I9 may takey the form of a pair of separate single phase rectiiiers, it is shown as a twin type tube with anodes 55 and 55 connected to the outer ends of the transformer secondary winding parts 5l and 52 respectively and with electricallyconnected cathodes 51 and 58 or a common cathode connected through a load resistor 59 to the transformer secandary junction or mid-terminal 53. Preferably,

`a smoothing condenser 6I is connected across the load resistor 59. A

The tube I9 may be a twin diode tube or, if desired, a twin triode tube may be utilized by tying the grids` 62` to the respective anodes 55 and 5B.

The twin rectier tube 2l is connected to the transformer I84 ina manner similar to the twin recti'er I9 and has an output or load resistor 63 also connected in a similar manner. The load resistors 59 and 63 are connected in series with their ends of like polarity connected together to form a differential or series opposed circuit. For example, the negative ends of the resistors'59 and 63 may be connected by a conductor 64 and the remaining ends of resistors 59 and 63 may be connected to the output terminals 22.

When the input terminals I3, I4 and I5, I6

'are energized, the control grids of the tubes Il and I2 will likewise be energized during the .positive half cycles of their respective input voltages. Considering, for example, the tube II dur- 'ing the positive half cycles of the reference voltage, the grid. 33 will be more strongly positive and relatively greater current will iiowthrough the part 41 of the primary winding of the transformer I1. Likewise during positive half cycles of the `signal voltage the grid 31 will be more strongly positive and stronger tube current will ow through the part 48 of the primary winding of transformer I1. The currents in the two parts 41 and 48 will flow in opposite directions to that if the reference voltage and the signal voltage are in phase, the amplified currents in the 180 out of phase, however, the opposition eiect is reduced to a minimum and relatively greater current ows through the primary Winding of the transformer I1 during each half cycle. Such current flows in the winding parteI 41 and 48 during'altern'ate half-cycles since the grids 33 and 31 are alternately positive. Accordingly, voltage is induced in the secondary windings 5I and 52jduringeach half-cycle. Consequently, a rectified output occurs across the load resistor 59 since the center-tap transformer secondary winding and the bi-phase rectiiier I9 actin a conventional manner to produce a directv current through the resistor 59 proportional to voltage across the ends of the secondary windings 5I, 52.

Since the -input to one of the triode-units 45 and 46 has been reversed with respect' to the polarity of the corresponding input to one of the triode units 29 or 34, the currents in the current-combining tube I2 act in opposition in the transformer I8v when the currents in the tube II are aiding and vice versa. Consequently, for varying phase relationshipathc relative outputs from the secondary windings of the transformers I I1 and I8 vary in magnitude and polarity and likewise the voltages in the resistors 59 and 63 vary with the phase relationship. Thus, for a given phase relationship maximum current flows in the resistor 59 and minimum in resistor 63 and an output of given polarity appears at direct current output terminals 22. With a reverse in phase relationship the polarity reverses. For intermediate phase relationships, the relative durations of time that the grids 33 and 31, e. g., are simultaneously positive are varied and accordingly intermediate values of direct current output are obtained from the output terminals22'. The input voltages are combined vectorially.

In the arrangement of Fig. 2, there are a pair of push-pull connected current controlling devices 1I and 12 and a corresponding pair of pushpull connected current controlling devices 13 and 14. The tubes 1I to 14 are of the double input type and they may take the form of pentodes, for example One input may be through a set of Number 1 or control ,grids and the other input may be through a set of Number 2 or screen grids. The reference voltage input terminals I3 and I4 are coupled to one set ofV grids and the signal voltage input terminals I5 and I6 are cou-pled to the other set of grids. An amplifying and phase-splitting inversion circuit 15 is provided for .coupling one pair of input terminals to one set of grids supplying input voltages of vopposite phase to the two pairs of push-pull connected tubes 1I, 12 and which are connected to the output of the potentiometer 23, thus supplying potentials of opposite polarity to the control grids 15 and 11. The ends of the resistor 8| are connected also to the grids 18 and 19I of the 'tubes 18 and 14, but with polarity reversed. The'plate circuits of the tubes 1|-, 12.

avancee .the tube 1| but not in 13. and 14 are also push-pull connected vto a load resistor with two parts l2 and 83 having a junction terminal- 84 connected to thevpositive terminal of a power supply represented by a battery 85. Thus, the pair of tubes 1| and 12 is push-pull connected so that the resistors 82 and 83 form respective anode loads for the tubes 1| and 12. Likewise the pair of tubes 18 and 14 is push-pull connected and is in iirst pair of tubes.

parallel with the the tube 12. With reversal of phase. the current ilo'ws in the opposite tube and a reverse of voltage output takes place across resistors 82 and 83.

Th second pair of push-pull tubes 13 and 14 provides for ilow of current during the half cycles when neither of the tubes 1| and 12 is conductive. If the reference voltage and signal voltage are not exactly in phase or exactly out oi' phase, the grids of any tube will be simultaneously above cut-oif value for only a fraction of a cycle. Accordingly, the relative currents flowing in the tubes 1| and 12 will depend upon the phase relationship between the input voltages. For quadrature relationship. the currents will flow for equal periods of time in both tubes 1| and 12, and similarly in the tubes 13 and 14, resulting in balanced output and zero net output from th'e output terminals ||8 and ||9.

|02 connected to an output terminal |03 having phase relation opposed to that of the terminal 88 of the inversion circuit 15.

The inversion circuit 15 may comprise an initial splitting stages. V y

'Ihe stage |04 comprises a. current controlling device such as a triode vacuum tube |05 having a control electrode or grid |00 capacitively coupled to the signal voltage terminals |5\|8, an anode |05 to which is connected resistor |,01connected in series with the power supply |08. and

inversion stage |04 and amplifying a grounded cathode resistor |09. The grid circuit of tube |04 may include a grid leak resistor and the portion of the cathode resistor |09 between a tap H2 and the tube |04. For supplying a signal voltage of reversed phase to the inversion terminal 88, an amplifying stage ||8 and an electronic control device ||4 may -be interposed between the cathode resistor |09 and the inversion circuit output termina-188.' Likewise for supplying a signal voltage of the same phase as the terminal l5, an amplifying stage H5 and a control device 'H8 may be interposed between the anode resistor |01 of the tube |04 and the output terminal |03 of the inversion circuit 15.

The valves or control devices ||4 and y| I6 may take the form of beam-power vacuum-tube ampliers, if desired, having a common power supply Il'l. The supply ||1 is connected through the tubes I4 and ||8 to the inversion circuit output terminals 88 and |03, respectively, for energizing the pair of screen grids 88 and 81 andthe pai'ra of screen grids l0! and |02 of the tubes 1| to Direct current output terminals H8 and IIS may be connected at the ends of the load resistors-82 and 83, respectively.

As a result of the presence of two pairs of pushpull connected tubes, full wave action is provided by the phase responsive circuit. Considering only one pair of tubes, for example, the tubes 1| and 12, it will be observed that the reference voltage and the signal voltage are combined in one relationship in the'tube 1| and in the opposite relationship in the tube 12. For example, if the phase relationship is such that the voltages aid in the Atube 1|, they will act oppositely in the tube'12.

and vice versa. Assuming that the input voltages are exactly in phase or exactly in phase opposition, both grids of one of the tubes, such as tube 1|, will be energized simultaneously whereas only one of the grids of the lother tube 12 is energized. Accordingly, current will ilow in ool yduring the next half cycle the valve ||6 applies voltage through th'e terminal |03 to the screen grids |0| and |02 in parallel. Thus, as far asv the screen grids are concerned, the pairs of tubes 1I-12 and 13-14-are rendered capable of con` ducting during opposite half cycles of the signal voltage. l

.Since the connections of the control grids 18- 19 to the reference voltage input resistor 8| are opposite to the connections of the control grids lliv and 11 to the input resistor 8|, one or the other of the tubes 1| and 13 has its control grid 1S or 18 rendered positive by the input from the reference voltage. If the reference voltage and signal voltage are in ph'ase, current is supplied during each half cycle through one or the other of the tubes 1I and 13, producing a voltage drop in load resistor 82. However, if the reference voltage and signal voltage are out of phase, currents flow alternately through the tubes 12 and 14 instead, and current flows through the load resistor 83. Thus, the polarity of the output voltage between the direct current output terminals ||8 and ||9 depends upon the phase relationship between the signal voltage and reference voltage. For intermediate phase angles between zero and 180 current flows through both of the resistors 82 and 83 in relative amounts, depending upon the actual phase angle.

I have herein shown and particularly described certain embodiments of my invention and certain methods of operation embraced therein for the purpose of explaining its principle of operation and showing its application, but it will be obvious to those skilled in the art that many modifications and variations are possible, and I aim, therefore, to cover all such modifications and variations as fall within the scope of my inven-v tion which is dened in the appended claims.

What is claimed is:

l. A phase-responsive system comprising, in

, combination, rst and second pairs of input terbeing connected in push-pull but with .opposite pairs` of push-pull tubes for coupling l"put connections from said'phase splitter, means for*V coupling one of said output connections to the second control elements of said first pair of current controlling devices in parallel, and means the second output connection of said phasesplitting means to the second control elements of said second pair of current controlling devices in parallel, said pairs of current controlling' devices fhaving parallel load circuits,

whereby the lload current varies in magnitude and polarity with variations in phase relationship between voltages applied to the input terminals.'

2. A phase-responsive system comprising, in combination, two pairs of current controlling devices, each device having a pair of control elements for a connection to input circuits, means for supplying an input witha push-pull connection to one pair of current controlling devices and for also supplying the same input reversed in polarity with a push-pull connection to the second pair of current controlling devices, and" means for supplying a second input in parallel to all four of said current controlling devices, said pairs of current controlling devices having parallel output'circuits, vwhereby the output varies in magnitude and polarity with variations in phase relationship between the two said inputs to the current controlling devices.

3. A phase-responsive system comprising, in combination, rst and second pairs of input terminals, first and second pairs of current controlling devices, each device having a'first control element and a second control element, the pairs of first elementsbeing connected in pushpull but with opposite input polarities to one of said pairs of input terminals, and a phase splitter coupled between the other of said pairs of input terminals and the pairs of current controlling devices.

attaccaA 4. A phase-responsive system for comparing vltwo inputs "comprising, in combination. two pairs of current controlling devices, each device having a pair of control elements for a connection to input circuits, means for supplying one input with a push-'pull connection to one pair of current controlling devices and for also supplying f the same input reversed in polarity with a pushpull connection to. the other pair of current ccntr'olling devices, and means for supplying the other input to all of said vcurrent controlling devices.

, JAMES E. SHEPHERD.

REFERENCES CITED The following references are of Frecord inthe 4ille of this patent:

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